Spindle motor and recording disk drive having spindle motor

ABSTRACT

Using a simple and inexpensive method, a reliable spindle motor having a simple and inexpensive structure is afforded, in which contact failure of the FPC does not occur even when the motor undergoes external impact. An extending portion is provided radially outer side of an annular recess of a base. The extending portion has a step whose radially outer side is higher, and a through hole formed such as to pass through the base from its inside to outside. A FPC is disposed on an upper surface of a stator. The FPC is fixed to a lower surface of the base through the through hole. The bending height and the bending angle of the FPC are minimized by providing the step having appropriate height so that the FPC is not easily peeled off even when subject to external impact.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a spindle motor, more particularly, toan inner rotor type spindle motor which is required to be thinner, andto a recording disk drive having the spindle motor.

2. Description of the Related Art

In recent years, signal recording/reproducing devices such as hard diskdrives (HDDs, hereinafter) are incorporated in portable devices such ascell phones, and this tendency accelerates size and thickness reductionsof HDDs from year to year. In addition, when the signalrecording/reproducing devices such as hard disk drives are incorporatedin the portable devices, as compared with a conventional case where theyare incorporated in personal computers, it is required to largelyenhance a resistance against an external impact such as a drop impact.In correspondence with these requirements of the HDD, a spindle motor tobe incorporated in the HDD is also increasingly required to reduce itssize and thickness and to enhance the impact resistance. To meet therequirements, types of spindle motors are moving to an inner rotor typespindle motor in which a stationary member surrounds a rotor and a fluiddynamic pressure bearing utilizing dynamic pressure generated by fluid.

According to this inner rotor type spindle motor, although the impactresistance around the bearing can be enhanced, the enhancement of theimpact resistance against the mounting manner of other portions,especially a flexible printed circuits (FPC, hereinafter) is not yetsufficient. For example, it is necessary to install wires from inside tooutside of a base using the FPC for supplying power, but since it isnecessary to install the wire in a narrow space, a FPC disposed on astator is bent at a sharp angle and fixed on a lower surface of the basewhen the FPC passes through a through hole of the base. If the FPC isstrongly bent, the FPC exhibits a great resilience for returning the FPCto its original state, a force for always separating the base isstrongly applied to a lower surface of the base that is a mountinglocation of the outside of the base. Therefore, when an external impactis applied when a portable device falls, there is a high risk that theFPC is easily peeled off from the base and a contact failure occursbetween an external power supply and an external connect portion formedon a lower surface of the base of the FPC. It can also be contemplate toincline a hole so that a wire can be installed easily, but it isdifficult to form a hole which is inclined with respect to a small base,and there is a drawback that the cost is increased correspondingly.

BRIEF SUMMARY OF THE INVENTION

The present invention has been accomplished in view of a contact failurewhich occurs when the above-described impact is applied, and it is anobject of the invention to provide a reliably spindle motor in which acontact failure of a FPC does not occurs by devising easy andinexpensive method and structure.

As a preferred embodiment, in the spindle motor of the presentinvention, a base has an annular recess which opens upward in an centeraxis direction. The recess accommodates a stator. An extending portionis provided on the base on a radially outer side of the annular recess.The extending portion has a step and a through hole. A portion of thestep on the radially outer side is higher than a portion of the step onthe radially inner side. The through hole penetrates the base frominside to outside. With this structure, a FPC whose one end is connectedto an upper surface of the stator does not pass through the through holeand is not largely bent during wiring process in which the FPC is fixedto the lower surface of the base through the through hole. It ispreferable that the open end surface of the through hole is providedwith the inclined surface so that wire can be installed more smoothly.Bending resilience acting in a direction in which the FPC is peeled offis restrained from being generated, the FPC is strongly fixed.Therefore, the FPC can not be peeled easily even when an external impactis applied, and connection between the FPC and an external power supplycan be maintained.

As another preferred embodiment, in the recording disk drive of thepresent invention, the spindle motor of the invention is used. Thus,connection between the FPC and an external power supply can bemaintained even when an external impact is applied. Therefore, it ispossible to provide a reliable recording disk drive.

The above and other objects and effects of the present invention will beapparent from the following detailed description.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic sectional view showing a recording disk drive of afirst embodiment of the present invention;

FIG. 2 is a schematic vertical sectional view showing the spindle motorof the first embodiment of the invention;

FIG. 3 is a diagram showing peripheries of a base and a stator of thespindle motor of the first embodiment of the invention;

FIG. 4 is an enlarged diagram of an essential portion of the spindlemotor of the first embodiment of the invention;

FIG. 5A is an enlarged diagram of an essential portion of a conventionalspindle motor;

FIG. 5B is an enlarged diagram of an essential portion of the spindlemotor of the first embodiment of the invention;

FIG. 6 is an enlarged diagram of an essential portion of a spindle motorof a second embodiment of the invention; and

FIG. 7 is an enlarged diagram of an essential portion of a spindle motorof a third embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION Best Mode for Carrying Out theInvention

A spindle motor and a recording disk drive having the spindle motoraccording to an embodiment of the invention will be hereinafterexplained with reference to FIGS. 1 to 7. In the description of theembodiments of the invention, a vertical direction of each drawing isdescribed as a “vertical direction” but this does not limit a directionin an actual mounted state.

First Embodiment

Recording Disk Drive

One mode of the embodiment of a recording disk drive 100 according tothe present invention will be explained with reference to FIG. 1. FIG. 1is a sectional view of the recording disk drive 100.

The recording disk drive 100 is configured such that it is accommodatedin a box-like housing 110. A clean space having extremely little dust isformed in the housing 110. A spindle motor 130 having a disk-like harddisk 120 which rotates at high speed around a rotation center axis isdisposed in the space. The housing 110 and a later-described base 10 mayintegrally be formed together.

A head moving mechanism 140 which swaps information with the hard disk120 is disposed in the housing 110. The head moving mechanism 140includes a magnetic head 141 which writes and reads information on thehard disk 120, an arm 142 which supports the magnetic head 141, and anactuator 143 which moves the magnetic head 141 and the arm 142 to adesired position on the hard disk 120.

If the spindle motor of the present invention is applied as the spindlemotor 130 of the recording disk drive 100, it is possible to reduce sizeand thickness of the recording disk drive 100 while securing sufficientfunction, and to provide a reliably recording disk drive having highdurability.

Structure of Spindle Motor

Next, with reference to FIG. 2, the entire structure of the spindlemotor of the invention will be explained. FIG. 2 is a schematicsectional view showing one mode of the embodiment of the spindle motorof the invention. A term “vertical direction” in the specification meansa vertical direction in FIG. 1.

In the spindle motor shown in FIG. 2, a base 10 is formed ofnon-magnetic steel plate by means of plastic working such as pressworking, and the base 10 is formed with an annular recess 10 a. Therecess 10 a is surrounded in its circumferential direction by twocylindrical wall surfaces of a small-diameter sidewall 10 b and alarge-diameter sidewall 10 c. The small-diameter sidewall 10 b and thelarge-diameter sidewall 10 c are coaxial with each other and havedifferent radii. The recess 10 a is formed into an annular groove-likeshape whose lower side in a rotation axis is closed with a bottom 10 dand whose upper side in the rotation axis is opened.

An annular stator 20 is fitted into and fixed to an inner peripheralsurface of the large-diameter sidewall 10 c such that the annular recess10 a is coaxial with the rotation center axis. A substantiallycylindrical bearing holding member 30 is coaxially fitted to and fixedto an inner peripheral surface of the small-diameter sidewall 10 b. Acylindrical bearing sleeve 31 is coaxially fixed into and fixed to aninner peripheral surface of the bearing holding member 30.

A shaft 41 is inserted into the bearing sleeve 31 with a fine gapinterposed therebetween such that the shaft 41 is coaxial with therotation center axis. The shaft 41 is rotatably supported throughlubricating fluid charged into the fine gap. An upper portion of theshaft 41 is formed into rotor hub 40. The rotor hub 40 is made of strongmagnetic material, and is formed into a substantially cylindrical shapeprovided at its radially outward portion with a cylindrical portion 42.The rotor hub 40 surrounds upper portions and outer peripheries of thebearing holding member 30 and the bearing sleeve 31.

A thrust plate 50 which is greater than an outer diameter of the shaft41 is fixed to a lower end of the shaft 41. The bearing holding member30 is provided at its lower portion with a plate-fixing portion 32. Adisc-like plate 60 is fixed to the plate-fixing portion 32 so that thebearing holding member 30 is formed into a bottomed container structure.A periphery of the thrust plate 50 is surrounded by the bearing holdingmember 30, the bearing sleeve 31 and the plate 60.

A dynamic pressure generating groove is formed in at least one of anouter peripheral surface of the shaft 41 and an inner peripheral surfaceof the bearing sleeve 31. The shaft 41 is supported in the radialdirection by a fluid pressure generated by the dynamic pressuregenerating groove. A dynamic pressure groove is formed in at least oneor more of a lower surface of the bearing sleeve 31, an upper surfaceand a lower surface of the thrust plate 50 and an upper surface of theplate 60. The shaft 41 is supported in the axial direction by a fluidpressure generated by the dynamic pressure generating groove.

A disk-mounting surface 43 is formed on an outer peripheral surface of acylindrical portion 42 of the rotor hub 40. The disk-mounting surface 43projects radially outward. A magnetic cover 44 projecting radiallyoutward is formed on an outer peripheral surface of the disk-mountingsurface 43. A rotor magnet 70 is fixed to and mounted on an outerperipheral surface of the cylindrical portion 42 located below thedisk-mounting surface 43. An upper portion of the rotor magnet 70 iscovered with a magnetic cover 44, and an outer peripheral surface of therotor magnet 70 is opposed to the stator 20 at a small distance.

A FPC 80 is fixed to and disposed on an upper side of the stator 20, anda shield plate 90 is disposed above the FPC 80.

If the stator 20 is energized by an external power supply (not shown)through the FPC 80, a magnetic field is formed around the stator 20. Apredetermined rotation torque is obtained by interaction between themagnetic field and the rotor magnet 70, and it is rotated and driven.

Essential Portion

Next, a relation between a periphery of the stator 20 and the base 10which are essential portions of the invention will be explained withreference to FIGS. 3 to 7. FIG. 3 shows a relation between the stator 20and the FPC 80. FIG. 4 is an enlarged diagram of an essential portion ofFIG. 2. FIG. 5 show the embodiment of the invention shown in FIG. 4 andan example of the conventional structure in comparison, wherein FIG. 5Ashows the conventional example and FIG. 5B shows the present invention.FIGS. 6 and 7 show other embodiments of the essential portion of theinvention.

As shown in FIG. 3, the stator 20 is formed in such a manner that aplurality of thin plates are laminated and mounted on one another, eachthin plate has a plurality of teeth 22 projected from an annular coreback 21 radially inward, the teeth 22 are provided at equal distancesfrom one another in the circumferential direction, and a winding 23 iswound around each tooth 22. The spindle motor of the invention is athree-phase drive motor, the three phases are U-phase, V-phase andW-phase. The spindle motor includes a common phase as a connection ofthese phases. Therefore, the number of terminals of the winding 23 isfour. Radially inwardly projecting projections 24 project fromrespective intermediate positions between adjacent teeth 22 in thecircumferential direction. Each projection 24 is formed with a circularthrough hole 25. A substantially annular insulator 26 made of insulatingmaterial is fitted into and fixed to the holes 25. The insulator 26functions to cover an interior of the core back 21 from above, andretain a crossover of the winding. The FPC 80 is fixed to the windings23 by means of adhesive such as to cover an upper side of the core back21 of the stator 20 and spaces between adjacent teeth 22. The FPC 80 isdisposed at a location out from a moving range of the head movingmechanism 140. The FPC 80 is of substantially arc shape, and is providedwith four projections 81 projecting radially inward. Each projection 81is formed at its central portion with a land 81 a. The windings 23 areconnected to and fixed to the lands 81 a through conductive members suchas solder to electrically connect the windings 23 and the FPC 80. Thisis because that if the FPC 80 is disposed below the stator 20, itbecomes difficult to fix the lands 81 a and the windings 23 to eachother. If the FPC 80 is disposed above the stator 20, on the other hand,it becomes easy to fix the lands 81 a and the windings 23 to each other.A main body 82 of the FPC 80 has such a wiring structure that the fourlands 81 a become land wires 81 b, respectively, and each land wire 81 bis connected to an external connecting portion 83 provided above themain body 82 which is wider than a straight portion 82 b through an arcportion 82 a and a straight portion 82 b. The external connectingportion 83 and the external power supply (not shown) are connected toeach other and are energized, the windings 23 are energized.

As shown in FIG. 4, the base 10 is provided with an extending portion 11extending radially outward. The extending portion 11 is located on aradially outer side as compared with the annular recess 10 a as viewedfrom a center axis. The extending portion 11 is provided with a step 12.A step-like shield plate fixing portion 13 is provided on a furtherradially outer side for fixing an annular shield plate 90 which coversthe extending portion 11 and the stator 20.

The step 12 is formed with a through hole 12 a having almost the samewidth as that of the external connecting portion 83. The straightportion 82 b and the external connecting portion 83 of the FPC 80 areinserted into the through hole 12 a, and the FPC 80 is disposed on alower surface of the extending portion 11 located outside of the base10. Therefore, the FPC 80 disposed on the upper surface of the stator 20is first temporarily attached to an upper surface of the extendingportion 11, the FPC 80 passes through the through hole 12 a and comesoutside from the inside of the housing 110, and is lastly fixed to thelower surface of the base 10. When the FPC 80 and the lower surface ofthe base 10 are to be fixed to each other, an adhesive is previouslyapplied to the FPC 80. With this, they can easily be fixed to eachother. If the adhesive is charged such that the upper surface of the FPC80 and the through hole 12 a of the extending portion 11 are filled withadhesive, the extending portion 11 and the FPC 80 can reliably be fixedto each other. With this, the FPC 80 can come into direct contact withthe external power supply, and electricity can be supplied from theexternal power supply. If the extending portion 11 is provided with thestep 12, it is possible to suppress the axial bending of the FPC 80, andthe bending angle of the FPC 80 can be reduced. Thus, a resiliencegenerated when the FPC 80 is bent can be reduced. With thisconfiguration, the external connecting portion 83 of the FPC 80 does notcome out from the extending portion 11 even when external impact isapplied. Thus, it is possible to provide a reliable spindle motor.Especially, it is preferable that a radially inner side of the step 12as viewed from the rotation center axis is low and a radially outer sideof the step 12 is high so as to reduce the axial bending of the FPC 80.

Essential portions of the present invention will be explained mainlybased on differences caused by structures concerning bending of the FPC80 by comparing bending angles and bending heights of the FPC 80 in aconventional structure and the embodiment of the present invention withreference to FIG. 5.

In the conventional structure shown in FIG. 5A, the extending portion 11of the base 10 is provided with a through hole 12 b in the direction ofthe rotation center axis.

Here, L1 and L2 are bending heights from a lower surface of the FPC 80mounted on the lower surface of the base 10 to an upper surface of theFPC 80 fixed to the extending portion 11. Further, φ1 and φ2 are bendingangles formed between the FPC 80 mounted on the lower surface of thebase 10 and portions of the FPC 80 which pass through the respectivethrough holes 12 a and 12 b.

In the conventional structure, a vertical difference between the uppersurface and the lower surface of the extending portion 11 is great andthus, the bending height L1 of the FPC 80 is increased correspondingly.Further, to prevent dust from entering from the outside of the HDD, itis necessary to reduce a radial opening as viewed from the rotationcenter axis of the through hole 12 b. Therefore, the bending angle φ1 isincreased consequentially. If the bending height L1 and the bendingangle φ1 are increased, the bending resilience of the FPC 80 is alsoincreased. Thus, a force applied to the external connecting portion 83which is fixed to the lower surface of the base 10 is increased, and theFPC 80 is prone to be peeled off.

In comparison with the conventional structure shown in FIG. 5A,according to the embodiment of the present invention shown in FIG. 5B,the vertical difference between the upper surface and the lower surfaceof the extending portion 11 is reduced by providing the step 12, i.e.,by forming the step such that a portion of the upper surface of theextending portion 11 on the radially outer side as viewed from therotation center axis becomes higher than a portion of the upper surfaceof the extending portion 11 on the radially inner side. With this, thebending height L2 and the bending angle φ2 can be reduced. Therefore,the bending resilience of the FPC 80 is reduced, a force applied to theexternal connecting portion 83 which is fixed to the lower surface ofthe extending portion 11 becomes smaller and thus, the FPC 80 becomesless prone to be peeled off. As a result, the contact failure of theexternal connecting portion 83 is less prone to occur, and a reliablyspindle motor can be provided. The step 12 can be formed by reducing theupper surface side height of the extending portion 11 such that aportion of the upper surface on the radially inner side becomes lowerthan a portion of the upper surface on the radially outer side as viewedfrom the rotation center axis.

It is preferable that an axial height position of an end surface of anupper portion of the large-diameter sidewall 10 c constituting theannular recess 10 a of the base 10 is higher than an axial heightposition of an end surface of an upper portion of the core back 21 ofthe stator 20, and is lower than an axial height position of the uppersurface of the winding 23. If the axial height position of the endsurface of the upper portion of the large-diameter sidewall 10 c iswithin this range, an axial height position of the through hole 12 aformed in the extending portion 11 is substantially equal to an axialheight position of the FPC 80. Thus, it is possible to fix the externalconnecting portion 83 to the lower surface of the extending portion 11without bending the FPC 80 almost at all.

Second Embodiment

Next, a second embodiment will be explained with reference to FIG. 6.Since a motor of this embodiment has basically the same structure asthat of the first embodiment, only different portions will be explained.

As shown in FIG. 6, in the second embodiment, a through hole 14 isoriented in the radial direction of the large-diameter sidewall 10 c.With this, it is possible to fix the external connecting portion 83 tothe lower surface of the extending portion 11 without bending the FPC 80almost at all. Thus, it is unnecessary to form the step 12 and it ispossible to thin the base 10. This structure is suitable when there is amargin in the axial height between the upper surface of the stator 20and the disk-mounting surface 43 of the rotor hub 40, or when a spacefor providing the step 12 is not enough.

It is difficult to form the through hole 12 a provided in the step 12 orthe through hole 14 provided in the large-diameter sidewall 10 c afterthe step 12 of the base 10 and the annular recess 10 a are formed, andthe operation efficiency is deteriorated. Thus, it is preferable thatthe through hole 12 a or the through hole 14 is formed before the step12 of the base 10 and the annular recess 10 a are formed.

A recessed guide groove 17 having substantially the same width as thatof the FPC 80 is provided on the upper surface of the extending portion11 forming the step 12 at a location on the radially inner side than thethrough hole 12 a as viewed from the rotation center axis. With this, itbecomes easy to position the straight portion 82 b of the FPC 80. As aresult, it becomes easy to position the external connecting portion 83.If the FPC 80 is deviated in position, a large force is applied to theFPC 80 and there is a danger that the FPC 80 is peeled off, but if theFPC 80 is positioned by the recessed guide groove 17, it is possible toprevent the above inconvenience from being generated.

According to the second embodiment, the same effect as that of the firstembodiment can be obtained.

Third Embodiment

Next, a third embodiment will be explained with reference to FIG. 7.Since a motor of this embodiment has basically the same structure asthat of the first embodiment, only different portions will be explained.

As shown in FIG. 7, in the third embodiment, an inclined surface 12 c isprovided on each of an upper surface of the through hole 12 a on theradially inner side and a lower surface of the through hole 12 a on theradially outer side as viewed from the rotation center axis. Each theinclined surface 12 c is inclined in such a direction that a diameter ofan end surface of the through hole 12 a is increased. This structure ispreferable because the bending angle of the FPC 80 can further bereduced. This effect can be exhibited only if the inclined surface 12 cis provided at least on a lower side of the step 12 (on radially innerside of the through hole 12 a as viewed from the rotation center axis inFIG. 7).

According to the third embodiment, the same effect as that of the firstembodiment can be obtained.

Although the embodiments of the spindle motor and the recording diskdrive having the spindle motor according to the present invention havebeen explained above, the invention is not limited to the embodiments,and the invention can variously be modified or improved withoutdeparting the scope of the invention.

For example, although the insulator 26 is used for retaining a crossoverof the winding 23 of the stator 20, the invention is not limited to thisonly if the crossover can be retained. More specifically, an innerperipheral edge of lowest one of the plurality of thin plates constitutethe stator 20 may be bent axially upward at an intermediate position inthe circumferential direction of the teeth 22.

Although the extending portion 11 of the base 10 is provided with thestep 12 in the embodiment, the invention is not limited to this shape.It is only necessary that the height of the upper surface of the throughhole 12 a on the radially inner side and the height of the lower surfaceof the through hole 12 a on the radially outer side as viewed from therotation center axis are different from each other. That is, an inclinedsurface may be formed instead of the step 12.

1. A spindle motor comprising: a rotor which is coaxially disposed witha center axis and which is provided at its outer periphery with a rotormagnet; a stator which surrounds the rotor and which is disposed at agap from the rotor magnet in a radial direction; a base having a recesswhich is opened upward for accommodating the stator, and when a side ofthe base opposed to the rotor is defined as inside and a side of thebase that is opposite from the inside is defined as outside, the recessis located inside; and a flexible circuit substrate having one endconnected to an upper side of the stator; wherein: the circuit substratehas an external connecting portion connected to an external powersupply, the base is provided, in a portion thereof radially outward ofthe recess as viewed from the center axis, with an extending portionhaving a through hole through which the external connecting portionpenetrates from the back side to the front side of the base, and asurface of the extending portion along an inward part of the base and towhich the circuit substrate is to be attached is formed so that aportion of the surface on the side radially outward of the location ofthe through hole is higher in the axial direction of the center axisthan a portion of the surface on the side radially inward thereof. 2.The spindle motor according to claim 1, wherein: the stator comprises acore back which is fitted into an inner peripheral surface of alarge-diameter sidewall of the recess formed in the base; teeth whichprojects from the core back radially inward and which are arrangedradially; windings wound around the teeth; and an axial height positionof an end surface of an upper portion of the large-diameter sidewall ofthe recess is equal to or higher than an axial height position of an endsurface of an upper portion of the core back when it is accommodated inthe recess, and equal to or lower than an axial height position of anupper surface of the winding.
 3. The spindle motor according to claim 2,wherein: a recessed guide groove is formed in an upper surface of theextending portion at a location radially inner side than the throughhole as viewed from the center axis, the recessed guide groove hassubstantially the same width as that of the circuit substrate; and astep is formed by the recessed guide groove between a portion of thespindle motor on a radially inner side than the through hole and aportion of the spindle motor on a radially outer side than the throughhole as viewed from the center axis.
 4. A recording disk drivecomprising: a recording disk having a magnetic recording layer; aspindle motor according to claim 3, for rotating the magnetic disk; amagnetic head which records information on the magnetic recording layerand which reproduces information recording on the magnetic recordinglayer; and moving unit which moves the magnetic head with respect to therecording disk.